(1) Field of the Invention
The present invention relates generally to screen printing and, more particularly, to a method and apparatus for screen printing a digitalized image on hard surfaces, such as glass or a mirror.
(2) Description of the Prior Art
The conventional technique for painting or decorating hard surfaces such as glass, a mirror or ceramic surfaces is by screen printing. In a typical screen printing operation, a separate screen is made for each color to be applied. A first screen is brought into registry with the glass or ceramic surface and a first color painted thereon. A second, third, and fourth screen, if necessary, each representing different colors, is then brought into registry with the surface and the additional colors painted or brushed thereon through the pattern in the screen. One serious disadvantage to such prior art screen printing techniques is halftones have not been achieved by screen printing and therefore true replicas of patterns or scenes have not been possible except by prohibitively expensive photographic means.
In the textile industry, the problems associated with screen printing have been overcome, to some extent, by a process known as "heat-transfer printing" in which a carrier consisting usually of paper or aluminum foil is printed with sublimable dyes temporarily affixed to the carrier by the use of binders. The carrier so printed is then laid with the printed side adjacent the fabric to be printed, and is then heated under pressure to a temperature in the range of 160.degree. C. to 220.degree. C. on the unprinted side of the carrier to sublime the dyes onto the fabric.
Heat-transfer printing techniques have been attempted onto a wide variety of sheet-like articles such as wood, metals, glass, ceramics, and certain synthetic resins by providing such articles with a surface layer or coating of a thermoplastic resin which adheres to the surface of the substrate and accepts the sublimable dyes. See German patent application DOS No. 2,642,350; French Pat. No. 2,230,794; and British Pat. No. 1,517,832. Similarly the surface of the article to be printed may be coated with a thermosetting resin (published European patent application No.14,901) which receives the dyes. Characteristic of all of the above approaches is that the transfer of the dyes by sublimation onto the thermosetting or thermoplastic resin is effected by means of heat supplied or generated by an external source.
While the above described techniques temporarily result in a somewhat satisfactory product with the dyes affixed to the resinous layer, which in turn is deposited on the glass or ceramic surface, serious problems have been observed. First of all, the thermosetting and/or thermoplastic resin tends to release from nonmetallic, inorganic surfaces such as glass or ceramic in the presence of moisture, such as would be present during washing, in bathrooms, or on items subjected to the outside elements. As the resinous coating peels away from the glass or ceramic surface, the decorative pattern vanishes. Further, disperse dyes tend to fade when subjected to sunlight. Also, when the disperse dyes are applied to a resinous coating on glass or ceramic surfaces, the disperse dyes oxidize after a short period of time. When oxidized, the surface becomes distorted and a large percentage of the inks rise to the surface and spread. These inks can be readily wiped off and the decorative pattern is lost.
One approach to avoiding these problems is described in U.S. Pat. No. 4,842,613, issued to Purser, in which the decorative pattern is applied to the back of a transparent sheet of glass and oxidation of the disperse dyes is prevented by applying a seal coat of a protective material such as lacquer, varnish or clear resin. However, this approach is much more costly than conventional screen printing.
Thus, there remains a need for a new and improved method and apparatus for screen printing images on either side of a sheet of hard material, such as glass or a mirror, while, at the same time, producing true replicas of patterns or scenes which have not previously been possible.
SUMMARY OF THE INVENTION
The present invention is directed to a method and apparatus for screen printing a converted digitalized image onto a hard surface, such as glass or a mirror. The apparatus includes a source for providing a conventional digitalized image, such as a digital scanner, digital camera or CD-ROM. A computer-assisted enhancer is connected to the digitalized image source and adapted to select the size and shape of the printed output comprising the digitalized image as a function of a preselected screen size for screen printing and to provide a converted digitalized image. In the preferred embodiment, the ratio of the mesh size to screen frequency (lpi) is about 3.
A dry film printer prints the converted digitalized image onto a transparent film which is used to prepare the screens for printing. In the preferred embodiment, the screen printing inks are selected from the group consisting of UV-cured, air-cured epoxy, and heat-cured lacquer for screen printing the converted digitalized image onto the hard surface.
Accordingly, one aspect of the present invention is to provide an apparatus for screen printing a converted digitalized image. The apparatus includes: (a) a source for providing a digitalized image; (b) a computer-assisted enhancer connected to the digitalized image source and adapted to select the size and shape of the printed output comprising the digitalized image as a function of a preselected screen size for screen printing and to provide a converted digitalized image; and (c) a printer for printing the converted digitalized image onto a transparent film.
Another aspect of the present invention is to provide a computer-assisted digitalized image enhancer for converting a digitalized image from a source of a digitalized image to a transparent film printer for subsequent use in screen printing. The apparatus includes: (a) an input means connected to the source for providing a digitalized image; (b) a processor connected to the input means and adapted to select the size and shape of the printed output comprising the digitalized image as a function of a preselected screen size for screen printing and to provide a converted digitalized image, wherein the ratio of the mesh size to screen frequency (lpi) is about 3; and (c) an output means connected to the processor for providing the converted digitalized image output to the printer for printing the converted digitalized image.
Still another aspect of the present invention is to provide an apparatus for screen printing a converted digitalized image. The apparatus includes: (a) a source for providing a digitalized image; (b) a computer-assisted enhancer connected to the digitalized image source and adapted to select the size and shape of the printed output comprising the digitalized image as a function of a preselected screen size for screen printing and to provide a converted digitalized image, wherein the ratio of the mesh size to screen frequency (lpi) is about 3; (c) a printer for printing the converted digitalized image onto a transparent film; and (d) an ink selected from the group consisting of UV-cured, air-cured epoxy, and heat-cured lacquer for screen printing the converted digitalized image onto a hard surface.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment when considered with the drawings.